1. Field of the Invention
The present invention relates to a method and device for the production of solid particles from a liquid and the separation of solid particles contained in a bath of refrigerating liquid. The method of producing and separating solid particles is intended for example for obtaining balls of ice for surface cleaning by projection of the particles, or for constituting solid products from aqueous mixture. Finally, the method of production and separation is provided for obtaining solid particles from liquids of which the latent heat of solidification is less than that of pure water.
2. History of the Related Art
French Patent 2 630 668 discloses a method and a device for producing balls of ice for surface treatments. The method consists in dispersing by gravity a spectrum of droplets of water in a column of cold gas, so that the droplets of water pass through said column of cold gas by gravity and cool, solidifyig superficially before dropping in a bath of refrigerating liquid where they are solidified entirely in the form of balls of ice. The device for carrying out the method comprises an exchange column supplied with cold gas and droplets of water which are regularly distributed via an injector to create a spectrum of droplets. The device also comprises a receptacle secured to the exchange column comprising a spray pipe for feeding the refrigerating liquid, a cone for receiving the balls of ice and an orifice for evacuating the balls of ice at the bottom of the cone.
The receptacle has a cylindro-conical form in which a refrigerating liquid such as liquid nitrogen is introduced with a view to completely solidifyig the droplets of water which pass therethough.
A phenomenon of heating will be noted, when the partially solidified droplets of water reach, at the end of their free fall, the surface of the refrigerating liquid, said phenomenon due to the evaporation of the liquid nitrogen. The phenomenon of heating retains each ball of ice in lift until it has attained the temperature of the gaseous nitrogen coming from the change of phase of the liquid nitrogen.
It will be noted that it is only after complete solidification of the ball of ice that it starts its descent by gravity to the bottom of the cylindro-conical receptacle the phenomenon of heating also provokes a high rate of occupation of the surface of the bath of liquid nitrogen, risking constituting either out-of-calibre balls or agglomerates which are highly detrimental to the manufacture of the balls of ice and to the extraction thereof at the Archimedean screw.
A second phenomenon which is detrimental in the manufacture of the balls of ice is noted, which is induced by the slight difference in density between the ice at -196.degree. and that of the liquid nitrogen, viz. respectively about 0.850 and 0.8068. The slight difference in density influences the dynamics of descent by gravity of the balls of ice, hence a strong tendency to constitute agglomerates at the surface of the bath of liquid nitrogen.
DE-A-2 805 676 discloses a method and a device for producing solid balls comprising a supply of cold gas, an agitator with blade, a receptacle and an Archimedean screw belonging to an extraction device. In this device, the movement of the liquid in the bottom of the receptacle is not directed downwardly, this resulting in risks of turbulences and choking.